The present invention concerns a method and an apparatus for detecting the fitness for circulation of a value document, such as a bank note.
Tactile structures are frequently provided on such value documents in order that persons with impaired or no vision, for example, can recognize the value documents on the basis of the tactile structures.
Such tactile structures are produced for example by means of embossing methods (e.g. engraving) and are well recognizable e.g. by means of mechanical scanning or a microscopic measuring method when the value document is in a new condition. Due to the circulation of the value document there occurs a degeneration of the embossed tactile structure so that, in the worst case, the embossing is no longer perceptible e.g. due to moisture, temperature, pressure and mechanical abrasion. There ultimately remains only a small haptic difference relative to the surroundings which, in the case of an ink-carrying engraving, is to be attributed to the microroughness of the engraving ink. With tactile structures that are based on a partial material thickening (e.g. screen printing, ink-jet printing, foil transfer), the preservation of tactile structures in circulation of the value document is guaranteed better. In this case, the reduction of the tactility in circulation happens e.g. through splintering off of the ink/foil or mechanical abrasion.